This invention relates to welding apparatus, and more particularly to welding apparatus suitable for welding together large molded articles having large and flat surfaces to be welded.
To weld together molded articles, for example plastic sheets formed by injection molding or extrusion molding or like techniques, it is usual to fuse the surfaces of the sheets to be welded together by a heated platen or the like and apply a pressure across superposed sheets. However, where the size of the molded articles is large, and the area to be welded is large but the width thereof is narrow, as in the case of welding molded articles having ribs on their surfaces, it is necessary to accurately adjust the relative positions of the articles and fusion allowance so as to uniformly heat the surfaces to be welded and to make constant the thickness of the fused or welded layer.
One example of such welded article is a pallet utilized to transport goods. A pallet is generally prepared by welding together two molded sheets each provided with a plurality of spaced parallel legs on the inner surface. Each leg is hollow and has a substantially rectangular cross-section having rounded ends. The wall of each leg projects as a rib from the inner surface of the sheet. To weld together two sheets, the rib shaped walls of corresponding legs are abutted against each other and then welded together.
In view of these requirements we have now completed novel welding apparatus wherein pressing plates of a special construction are used to apply a pressure across superposed molded articles which are heated and fused by a heated platen.